Polyamide in combination with polycarbonate, metal complex, polyisocyanating agent for polyester modification and rubber tire structures made therefrom

ABSTRACT

Relates to an improved rubber structure reinforced with an improved polyethylene terephthalate reinforcing fiber modified with a polyamide in combination with a metal complex or this twocomponent combination in combination with a polycarbonate, or the polyamide in combination with a polycarbonate and a polyisocyanating agent, the modifier being present with the polyester prior to fiber formation.

United States Patent Bhakuni et al. 1 Feb. 6, 1973 1 POLYAMIDE INCOMBINATION WITH [56] References Cited POLYCARBONATE, METAL COMPLEX,POLYISOCYANATING UNITED STATES PATENTS AGENT FOR POLYESTER 3,410,74911/1968 Chmiel ..161/92 MODIFICATION D RUBBER TIRE 3,446,766 5/1969Taylor ....260/45.75 C 3,359,235 12/1967 Brignac et a1... ....260/45.75C STRUCTURES MADE THEREFROM 3,426,100 2/1969 McDonough.... ..260/86O[75] Inventors: Roop S. Bhakuni, Copley; Joseph L. 3,563,849 2/1971 Ryeet a1. ..260/860 Co -many, Jr, Akron, both of Ohi 3,414,537 12/1968Dikotter et al ..260/45.75 C 3,558,553 1/1971 Hayes 260/4575 C [73]Assignee: Goodyear Tire & Rubber Company,

Akron Ohio Primary Examiner-Robert F. Burnett 2 Filed; March 22 197Assistant Examiner-C. B. Cosby AttarneyF, W. Brunner and V. G. Parker[21] Appl. No.: 126,964

[57] ABSTRACT [52] US. Cl ..57/l53,57/140 C, 57/149, Relates to animproved rubber Structure reinforced 156/1 10 C, 161/183, 161/190,161/241, with an improved polyethylene terephthalate reinforc- 161/248,ing fiber modified with a polyamide in combination led/231 C 260/3260/860 with a metal complex or this two-component combina- 260/863 tionin combination with a polycarbonate, or the 151] 25/08 B32b 27/02 B32b27/36 polyamide in combination with a polycarbonate and a {58] Field ofSearch; ..260/860, 45.75 C, 3, 863;

polyisocyanating agent, the modifier being present with the polyesterprior to fiber formation.

8 Claims, N0 Drawings POLYAMIDE IN COMBINATION WITH POLYCARBONATE, METALCOMPLEX, POLYISOCYANATING AGENT FOR POLYESTER MODIFICATION AND RUBBERTIRE STRUCTURES MADE THEREFROM This invention relates to an improvedrubber structure reinforced with an improved polyester reinforcing fiberbeing modified with (1) a polyamide in combination with a metal complexcompound or (2) the combination of 1) in combinationwith a polycarbonateor (3) a polyamide in combination with a polycarbonate and apolyisocyanating agent.

Pneumatic tires are being subjected to increasingly severe operatingconditions including high speeds and heavy loads. Rubber used in thetire is reinforced with such materials as rayon, nylon, polyester, wire,and glass fibers. Maximum reinforcement of the rubber is obtained with agiven fiber when maximum adhesion is produced between the rubber andfiber. Polyethylene terephthalate tire cords are particularly desirableto use as reinforcing elements because of their excellent dimensionalstability as shown by low growth or stretch during service. However, ithas been observed that in the environment of the rubber of a pneumatictire the heat generated under high speeds and heavy loads causes thepolyester cord to lose its durability, its tensile strength andultimately its adhesion to the rubber.

The chemical environment of the rubber of a tire is complex because manydifferent chemicals are needed in the construction of the tire in orderto obtain maximum tire performance. Because of this chemical complexityin the rubber of the tire and the severe heat developed during service,a variety of chemical reactions take place resulting in the degradationof the polyester cord.

Many attempts have been made 'to minimize these destructive forces andthe present invention is anadvance in solving the problems created bythese destructive forces. Prior attempts have been made by modifying therubber. Other attempts have been directed toward the adhesive. Thepresent invention is directed toward modifying the polyester cord.

It has now been discovered that a more thermally stable pneumatic tiremay be made when the rubber thereof is reinforced with a polyester cordmodified in the manner described herein.

The thermally stable tire is made possible by the discovery that apolyester cord used in the construction of the pneumatic tire can beprotected against tensile loss in the cord and degradation of theadhesive bond between the cord and the rubber by incorporating in thepolyester prior to fiber formation a critically small amount of acombination of modifiers. Combination modifiers usefulin this inventionare any of the following:

1. A polyamide in combination with a metal complex.

2. A polyamide in combination with a metal complex plus a polycarbonate.

3. A polyamide in combination with a polycarbonate plus apolyisocyanating agent.

It is believed that certain desirable reactions take place betweencertain undesirable by-products present in the polyester and the addedmodifiers to form a reaction product which is less detrimental to thepolyester at elevated temperatures than arethe by-products.

LII

175 C. or 200 C. and preferably higher, for example,

225 to 275 C. More specifically, polyamides which may be used includethose derived from dicarboxylic acids, for example, succinic acid,glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid,and

sebacic acid; and from diamines containing, for example, two to 10carbon atoms such as ethylene diamine, tetramethylene diamine,hexamethylenediamine, octamethylene diamine, l,4-di(methyla'mino)cyclohexane, etc; or the nylon may be derived from an omegaaminocarboxylic acid such as omega-aminobutyric acid, omega-aminopimelicacid, omega-aminocaproic acid, etc., or the lactams thereof. Thus themodifier may be those nylons referred to by number as 4, 5, 6, 7, 8, and11. The polyamide may be preferred from a lactam containing from four to11 carbon atoms. The polyamides desirably have molecular weights in therange of 16,000 to 30,000.

The polyamides, when used in combination with the other modifiers ofthis invention, may be used in an amount from about 0.01 part to about5.0 parts by weight per 100 parts of polyester.

The metal complex compound that may be used in combination with thepolyamide is any, complex the metal ion of which has an incompletelysatisfied d orbital and will further complex or coordinate withcompounds containing atoms like N, O, P, S and halogens and has astability (log k) constant for its ammonia and amine complexes ofbetween 5 and 25. The metal ions preferred in the metal complex of thisinvention include Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zr, Nb, Mo, Tc,

Ru, Rh, Pd, Ag, Hf, Ta, W, Re, Os, Tr, Pt, Au, Th, and

Pa. A preferred metal complex is copper dimethyldithiocarbamate havingthe general formula l 11 1 v -S- -N(CHa)z 2 The metal complex when usedin combination with the polyamide and other modifying agents may be usedin amounts from about 0.0001 part to 0.1 part by weight per parts ofpolyester. It is essential that when the metal complex and the othermodifiers are to be intimately blended with the polyester in the moltenstate which occurs in the range from about 270 C. to about 310 C. thatthe molten blend be maintained under a pressure of about 800 pounds persquare inch for not more than 10 minutes and preferably for from 1 to 4minutes and out of contact with oxygen, a condition present in meltspinning apparatus.

It is preferred to add the metal complex as a powder to the polyesterchips just prior to the introduction of the mixture into the extruderassociated with the spinning of the resulting molten mixture intofilaments.

The polyester modifier may be physically blended as a master batch assolids in a double cone dryer and then feeding the blend or separatematerials in an exact ratio at the throat of the extruder.

The polycarbonate, when added with the metal complex, may be present inan amount of between about 0.5 part to 2.5 parts by weight per 100 partsof polyester.

Any polycarbonate may be used as an additive or modifier or scavenger orprotective agent in combination with the polyamide and the othermodifiers or scavengers or protective agents for polyester tire cord.Broadly, the polycarbonates may be any derived from4,4'-dihydroxy-di(mononuclear aryl)-alkane and having a molecular weightbetween about 15,000 and about 80,000 and an intrinsic viscosity betweenabout 0.46 and about 1.2 as measured by dilute solution viscometry inmethylene chloride at 25 C. These polycarbonates can be prepared inaccordance with conventional methods including phosgenation in whichphosgene is blown into the 4,4-dihydroxydi(mononuclear aryl)-alkane inthe presence of. an aqueous solution of a caustic alkali and a solvent.The ester-interchange method may also be usedwherein a4,4'-dihydroxy-di(mononuclear aryl )-alkaneis reacted with a diester ofcarboxylic acid and as more fully described in British Pat. No. 772,627.

The polycarbonate used in the example below where indicated was apolyester of carbonic acid and bisphenol A known as [bis-(4-hydroxyphenyl)2,2,propane]and having the repeating unit structure part to about1.0 part per l parts by weight of polyester.

Any polyisocyanate or polyisocyanate generating compound collectivelyreferred to as polyisocyanating agent can be added to the polyesterchips prior to fiber formation. Typical polyisocyanating agents that maybe used arethose disclosed in U.S. Pat. No. 3,563,849, particularlyisocyanate generating compounds known as blocked isocyanates (alsoreferred to as polyurethanes) which include all reaction products of anisocyanate and a compound havinga hydrogen reactive with the isocyanategroup. Examples of the blocking compounds include monohydroxy compounds,especially primary and secondary alcohols, details of preparation beingdisclosed in U.S. Pat. No. 2,952,665 and 3,325,333, amines includingurea, primary and secondary mono and polyhydric phenols including phenoland resorcinol, amides as well as lactams, details of preparation beingdisclosed in Belgian Pat. No. 665,474, and resinous compositions whichhave an active hydrogen and will block an isocyanate. The preferred typeof resinous blocking agent is made by reacting an aldehyde with aresin-forming component such as urea, or a phenol, preferably apolyhydric phenol, such as resorcinol. Suitable aldehydes that may beused in forming a resin include formaldehyde, acrolein, glyoxahfurfural,crotonaldehyde, aldol and benzylaldehyde. Suitable phenols that may bereacted with oneof the aforementioned aldehydes, include phenol, cresol,catechol, phloroglucinol, saligenin, dibeta naphthol, xylenol,hydroquinone, resorcinol, orcinol, pyrogallol, beta-naphthol,aminophenol,

guaiacol, as well asurea and melamine. More detail of preparation isdisclosed in U.S. Pat. No. 3,268,467. The preferred polyisocyanatingagent used in the examples below where indicated is a polyester blockedpolyisocyanate known by the trademark Texin" 192A sold by Mobay ChemicalCompany and prepared by reacting 100 parts of the hydroxy polyesterprepared from reacting l1 mols of ethylene glycol with 10 mols of adipicacid, 9 parts of l,4-butandiol with 40 parts of 4,4-diphenyl methanediisocyanate having an HCl acidity of 0.017 percent to form thecorresponding polyurethane.

The polyester being modified is any fiber forming thermoplastic linearhigh molecular weight condensation polyester, and particularlypolyethylene terephthalate as well as polymers of cyclohexanedimethyleneterephthalate. These polyesters as well as copolyesters of aromaticdicarboxylic acids and particularly condensation products of ethyleneglycol with a mixture of terephthalic acid and isophthalic acid,ethylene glycol with terephthalic acid and another dibasic acid such asebisic or adipic acid or hydroxycarboxylic acid such as parahydroxybenzoic acid present in small amounts and polyesters of terephthalicacid with the glycol 1,4

bis(hydroxymethyl) cyclohexane. By linear terephthalic polyesters ismeant a linear condensation polyester comprising recurring glycoldicarboxyla'testructural units in which at least about percent of therecurring structural-units are units of the formula -o-o-0 o C-@C0whereinG represents a divalent organic radical containing from about twoto about eight carbon atoms which is attached to the adjacent oxygenatoms by saturated carbon atoms. The terephthalate radical may be thesole dicarboxylate constituent of the recurring structural units or upto about 15 percent of the structural units may contain other dicarboxylate radicals such as adipate, sebacate, isophthalate, 4,4 bibenzoateand hexahydroterephthalate. By high molecular weight is meant polyestershaving an intrinsic viscosity of at least 0.6 and preferably greaterthan 0.8 and as high as 1.5 as measured in a 60/40phenol/tetrachlorethane mixed solvent at 30 C. it is preferred that thepolyethylene terephthalate and other similar polyesters have a highmelting point which for polyethylene terephthalate is about 265 C.measured with a hot stage polarizing microscope. Generally the polyesterfibers of this in- EXAMPLES Parts by Weight 1(control) 2 3 l.Polyethylene terephthalate (polyester chips) a. IN. .6

2. nylon 66 (Zytel" 101 )(chips) 3. Copper dimethyldithiocarbamate(Cumate") (powder) 4. Polycarbonate (Merlon" M-39 (chips) 5.polyisocyanating agent (Texin 192A)(P0wder) The dried polyester chips(1) are tumbled with the modifiers (2), (3) and (4) in the combinationindicated for Examples 2, 3 and 4 until the mixture is substantiallyhomogeneous. Each blend is then melted in a conventional extruder headand each melt is then spun at a temperature of about 290 C. through a190 hole spinneret at a spinning speed of 150 yards per minute to give asingle spun yarn having a total denier of approximately 7,800 inaccordance with well-known practice used in the melt spinning art andshown in US. Pat. Nos. 3,091,510 and 3,097,056. The spun yarn is passedto a pair of rotating heated feed rolls and then passed around a pair ofheated draw rolls rotating at a speed to impart a draw ratio of about 6to l to give a total denier of approximately 1,300 and then wound on abobbin.

The modified polyester yarn had the following properties.

polyester (examples) control( 1) Ex. 2 Ex. 3 Ex. 4

l. Tenacity (grams/denier) 8.0 8.3 8.3 7.8 2. Break elongation 9.5 9.313.0 12.8 3. LV. .79 .78 0.79 0.80

of a 39.5 percent total solids of the 70/15/15 terpolymer ofbutadiene/styrene/vinyl pyridine and 64 parts of a 40.7 percent totalsolids of a 70/30 copolymer of butadiene/styrene, the mixture being in130.05 parts of water. The cords are passed through a dip tankcontaining this adhesive. The dipped cords are then dried at 450 F. andembedded in rubber compounds as shown below. Peel adhesion test is madeof a l-inch strip under static conditions at 250 F. Thermal stability ofthe cord is measured in terms of percent tensile retained by the airbomb (AB). Air bomb testing is done by heating the untreatedcordembedded in the rubber compound as shown below for 2.5 hours at 350F. under psi air pressure. The data obtained is listed in Table l. 4

TABLE l Peel Adhesion Mallory Percent Rubber reinforced with StripFatigue Tensile Cord from example Force Rating KC (2) Retained l.Control(no modifier 100 100 AB added) 2. nylon 66 +Cumate 98 200 l 12 ABmodified cord 3. nylon 66 'l-Cumate 1 17 97 100 AB polycarbonatemodified cord 4. nylon 66 +polycarbonate 201 97 AB polyisocyanatingagent modified cord Peel adhesion is determined in the following manner.Onto the surface of a 12 mil thick sheet (12" X 12'') of rubber (MRS) islaid the treated cords at the rate of 18 per inch which are then coveredwith a second sheet (12" X 12") of 12 mil gauge rubber (MRS). Thissandwich" arrangements of rubber cord and rubber is then doubled ontoitself with a piece of Holland cloth extending one inch into the doubledassembly from the open end from which assembly is clicked 1'' X 3"samples, which samples are then cured in a mold at 290 F. for 20minutes. The cured sample is then placed in an lnstron machine, heatedat 250 F. and the two strips of rubber separated by the Holland clothare then moved in opposite directions at the rate of 2" per minute todetermine the average orce.

The rubber component of the rubber structure ofthis invention may be anyrubber that is a stretchable composition having a tendency to return toits approximate original shape after being vulcanized, and particularlyany rubber that is used in the manufacture of tires and drive belts.Thus, the laminate of this invention may involve natural rubberotherwise known as Hevea Brasiliensis, or conjugated diene polymericrubbers made by polymerizing butadiene-l ,3, isoprene, 2,3- dimethylbutadiene-1,3, and mixtures of these conjugated dienes as well ascopolymers of these diene monomers with up to 50 percent of compoundswhich contain a CH =C= group and which are copolymerizable withbutadiene-1,3 where, for example, at least one of the valences isattached to an electronegative radical, that is a radical whichincreases the polar character of the molecule such as vinyl, phenyl,nitrile and carboxy radicals. Examples of the diene rubbers arepolybutadienes including the stereospecifics, polyisoprenes includingthe stereospecifics, butadiene/sytrene copolymers, also known as SBR,and

butadiene/acrylonitrile copolymers also known as NBR.

The control and modified polyester cords of this invention are embeddedin rubbercompounds in accordance with the following formula:

Parts by weight Ingredients Amount May be Used Used 1. Natural RubberUsed Used 1. Natural Rubber 70 0-100 2. OE/SBR 1778(styrenelbutadiene-l,3

23.5/76.5 copolymer) (plus 37% parts oil per 100 SBR 27.5 100-0 3. Cis1,4-polybutadiene 10 50 4. Carbon Black (Reinforcing agent) 40 25-100 5.Zinc Oxide (Activator of Cure) 4- 2-10 6. Stearic Acid (Activator ofcure) 2 1.5-3.0 7. Primary Accelerator (2,2-dlthlobisbenzothiazole) 1.25.5-3 .0 8. Pine Oil (Softener) 2-50 9. Secondary Accelerator(tetramethyl thiuram disulfide) .10 .05 l .0 10. Antioxidant a 0 .14 1l. Sulfur (Vulcanizing agent) 2.5 1.0-6.0

ln compounding the rubber stock in accordance with" the formulation setforth above, a master batch of ingredients (1) and (2) are made with thecarbon black and mixed on a mill to a temperature of about 1 10 C. andmay be mixed at a temperature as high as 140 C. The resulting carbonblack master batch is then cooled and the remaining compounds are mixedinto the batch in the order indicated above to a temperature of about 70C. and may be mixed at a temperature as high as 100 C.

The rubber structure of this invention may be prepared by first coatinga reinforcing fabric with the rubber and then using the rubber coatedfabric to make any desired structure as, for example, a pneumatic tire.The rubber will be compounded in the manner set forth above. Thereinforcing fabric may be used without any previous treatment, and underthese conditions the fabric is known as grey cord indicating that notreatment in the form of an adhesive composition has been applied to thesurface of the cord. Thus, the presentinvention may be used in themanufacture of a pneumatic tire of conventional present day design asshown, for example, in such U.S. Pat. Nos. as 3,157,218; 3,160,191,3,160,192; 3,217,778; 3,225,810; 3,225,812; 3,244,215; 3,253,633 and3,253,638 all of which show a vulcanized rubberized fabric carcass ofgenerally torodial shape having a tread portion superimposed and bondedto the crown area of the carcass and plies of rubberized fabric formingsidewalls extending from the tread over the carcass to the bead portion.

While certain representative embodiments and details have been shown forthe purpose of illustrating the invention, it will be apparent to thoseskilled in this art that various changes and modifications may be madetherein without departing from the spirit or scope of the invention.

What is claimed is:

1. In a heat stable structure comprising a heat stable polyester tirecord bonded to natural or diene synthetic rubber by means of an R/F/Ladhesive, the improvement wherein the cord is made of polyethyleneterephthalate fibers melt spun from a melt composition resulting frommelting a physical mixture comprising polyethylene terephthalate havingan [.V. of at least 0.6 and not greater than 1.5, from about 0.01 partto about 5.0 parts of a polyamidehaving a melting point in excess of 175C., from about 0.0001 part to about 0.1 part of copperdimethyldithiocarbamate, all parts being by weight per parts ofpolyethylene terephthalate.

15 000 to about 80,000.

4. The structure of claim 3 wherein .the polycarbonate is the reactionproduct of carbonic acid and his phenol A and has the repeating unit CHawherein n has a value from about 10 to 400.

5. in a heat stable structure comprising a heat stable polyester tirecord bonded to natural or diene synthetic rubber by means of an RIF/Ladhesive, the improvement wherein the cord is made of polyethyleneterephthalate fibers melt spun from a melt composition resulting frommelting a physical mixture comprising polyethylene terephthalate havingan l.V. of at least 0.6 and not more than 1.5, from about 0.01 part toabout 5.0 parts of a polyamide having a melting point in excess of C.,from about 0.5 part to about 2.5 parts of a polycarbonate having therepeating unit wherein n has a value from about 10 to 400 and from about0.01 part to about 2.0 parts of an organic polyisocyanating agent, allparts being by weight per 100 parts of polyethylene terephthalate.

6. The structure of claim 5 wherein the polyisocyanating agent in thecomposition is a blocked isocyanate.

7. The structure of claim 6 wherein the isocyanate is blocked with ablocking agent selected from the 'group consisting of primary andsecondary alcohols, monohydric and polyhydric phenols, amines, amides,lactams, and resinous reaction products of an aldehyde and a componentselected from the group consisting of I urea, phenol, and resorcinol.

8'. The structure of claim 7 wherein a polycarbonate derived from a4,4'4,4-dihydroxy di(mononucleararyl)-alkane is present in the mixturein an amount up to about 2 parts per 100 parts of polyester.

* l i I

1. In a heat stable structure comprising a heat stable polyester tirecord bonded to natural or diene synthetic rubber by means of an R/F/Ladhesive, the improvement wherein the cord is made of polyethyleneterephthalate fibers melt spun from a melt composition resulting frommelting a physical mixture comprising polyethylene terephthalate havingan I.V. of at least 0.6 and not greater than 1.5, from about 0.01 partto about 5.0 parts of a polyamide having a melting point in excess of175* C., from about 0.0001 part to about 0.1 part of copperdimethyldithiocarbamate, all parts being by weight per 100 parts ofpolyethylene terephthalate.
 2. The structure of claim 1 wherein thepolyamide is a linear condensation superpolymer of hexamethylenediamineand adipic acid.
 3. The structure of claim 1 the composition alsocontaining from about 0.5 part to about 2.5 parts of a polycarbonatehaving a molecular weight from about 15,000 to about 80,000.
 4. Thestructure of claim 3 wherein the polycarbonate is the reaction productof carbonic acid and bis phenol A and has the repeating unit wherein nhas a value from about 10 to
 400. 5. In a heat stable structurecomprising a heat stable polyester tire cord bonded to natural or dienesynthetic rubber by means of an R/F/L adhesive, the improvement whereinthe cord is made of polyethylene terephthalate fibers melt spun from amelt composition resulting from melting a physical mixture comprisingpolyethylene terephthalate having an I.V. of at least 0.6 and not morethan 1.5, from about 0.01 part to about 5.0 parts of a polyamide havinga melting point in excess of 175* C., from about 0.5 part to about 2.5parts of a polycarbonate having the repeating unit wherein n has a valuefrom about 10 to 400 and from about 0.01 part to about 2.0 parts of anorganic polyisocyanating agent, all parts being by weight per 100 partsof polyethylene terephthalate.
 6. The structure of claim 5 wherein thepolyisocyanating agent in the composition is a blocked isocyanate. 7.The structure of claim 6 wherein the isocyanate is blocked with ablocking agent selected from the group consisting of primary andsecondary alcohols, monohydric and polyhydric phenols, amines, amides,lactams, and resinous reaction products of an aldehyde and a componentselected from the group consisting of urea, phenol, and resorcinol.